Manually Adding a Decimal Field to the Attributes Table

Question

I am fairly new to QGIS and search as I might in the manual, training manuals and widely on the net I can't find an in-depth explanation of how to set up a Decimal Number (real) field in my attribute table properly.

I have a number of vector layers, each with a polygon on them. I need to add a decimal field to manually insert a rate per 1,000 of the population. The number is more than likely going to be between n.n and nn.n

I have tried all sorts of different width and precision figures, but either the field is too small to take the number, or it is large enough, but I can't get a decimal point in there. Does this mean that the decimal number is less than one?

When I have entered some information into the cell and pressed Enter the cell always reverts to NULL.

Please help!

Thanks

Andy

Answer 1

To add a decimal column follow these steps:

1. Open feature table
2. Start edit session on feature
3. Click New column button
4. Enter the following (precision refers to number decimal places), see caption below

Then, manually add or calculate values into your new column

Answer 2

You can use "New Column" tool in attribute table of your layer.

Width represent the total number of digits. Precision represents the number of decimals

Examples:

Width 5 Precision 3

• -2.001
• 99.999

Width 3 Precision 1

• 0.1
• 1.2
• 99.9

Width 20 Precision 9

• 11123456789.123456789

If your calculations are getting NULL values, first try to save and refresh your table attribute.

If the problem persist, make sure that the output of your calculus is a number and not a text.